Fingerboard Radius Question

[Alexander Higgins]

This may be a dumb question:
If a fingerboard tapers from the bridge end towards the nut, doesn't sanding a consistent radius on it with a sanding block create a fingerboard with a tapering edge thickness? As the board gets narrower, the edges get closer to the center highpoint of the radius, and therefore higher along the arc of the radius. If the fingerboard is bound, how do you account for this effect? it seems like it would have to be a compound radius fingerboard to work. Am I thinking about this wrong, or does the sanding process by hand tend to cancel this out somehow?

[Eric Baack]

the edge just gets shorter as you move to the wider part of the neck. Not that big of a deal. Unless you want to taper the thickness of the neck as a whole as well.

[John Sonksen]

It does get slightly thinner towards the heel of the neck on the edges, but I don't think it matters. Every string follows its own path relative to the fretboard, not each other as far as string height is concerned. That said the two fretboards I've made were compound radius and the edge stays the same down the whole length.

I modeled a couple in solidworks awhile back to see just how much the edge thickness varies with continuous and compound radii, and was surprised by how little it changed on the continuous.

[Alexander Higgins]

I want to bind the neck, so I thought you'd notice the binding thickness changing more than if it was just a wood edge. I don't think I could pull off a compound radius with my beginners skill set, guess I'll have to live with it and hope it's subtle enough not to be noticeable. The binding will get sanded with the fingerboard, so at least it will be a continuous taper. Thanks all.

[David King]

There is nothing much to "pull off" with a compound radius. Just taper your fingerboard sides and make a line down each side about 1/16" below the top edge. I use a block plane to rough in the facets what correspond to the string paths and then use a flexible scraper to knock down the points and give it a nice gradual arc. As long as you understand what wood you need to remove which you obviously do then it should be easy to get there. Granted a long belt sander is a very quick way to get there but the faster the tool is -the faster it makes mistakes.

[Barry Daniels]

You won't notice the slight tapering.

[TyDonald]

I sand the radius into my fretboards. I've noticed a tapering but since I'm working the radius in, I just sand a little more toward the nut and eyeball the edge.

[Henrique Schneiter]

Not a dumb question at all.

With a constant radius and a tapering fingerboard width, the thickness on the edges will taper as well. It's not much but can be noticeable, particularly if you have a tight radius and binding.

Four solutions as I see:

1- Use a compound radius.
2- Sand the upper part of the neck more (towards the nut), as Ty said.
3- Pre-taper the fingerboard thickness, before gluing to the neck or before radiusing.
4- Cut the binding channel AFTER you radius the fingerboard.

On that neck shown I used the latest, but it wasn't exactly easy.

[Henrique Schneiter]

By the way, the picture may give the impression that the binding is getting thinner towards the body, but it doesn't! It's just optical illusion from the perspective. I just don't have a better picture now anyway.

[Andy Birko]

it seems like it would have to be a compound radius fingerboard to work. Am I thinking about this wrong, or does the sanding process by hand tend to cancel this out somehow?

As everybody else mentioned, you're absolutely correct. The correct compound radius will indeed give you a constant height fretboard edge. E.g. for a 25.34″ scale, if you chose 1.75″ nut, 2.25″ 14th fret and a 12″ radius at the nut, you need a radius of about 19.7″ at the 14th fret to get a constant edge height. Very easy to do with CNC'd fretboards .